The preimplantation period of mammalian development is notable for the many crucial events that must occur in order to permit the developmental program to be executed correctly. Many such events have lasting effects on the pattern of gene expression and success of development in the embryo and even on gene function in the adult animal. Because of the importance of these early events to successful embryogenesis, an understanding of the molecular changes that occur during normal preimplantation development is of fundamental importance to the field of mammalian embryology. While preimplantation embryogenesis has been studied in detail in such species as mouse and rabbit, very little is known about preimplantation embryogenesis in primates. A detailed knowledge of the preimplantation period for primate embryos and molecular tools for its study are becoming increasingly in demand, particularly in the area of human reproductive medicine. Improvements in the rates of success of, e.g., in vitro fertilization and in vitro oocyte maturation may be sought through improvements in methods for in vitro culture of oocytes and embryos. The identification of specific gene products that are indicative of good oocyte and embryo health will be useful in the selection of embryos for implantation. New methods for preimplantation genetic diagnosis can also become available if a gene associated with a given disease is known to be expressed during the preimplantation period. Ethical and legal constraints preclude experimental analyses of human embryos. Detailed studies focusing on a suitable non-human primate embryo model have been prevented by limited access and great costs of obtaining these embryos. To increase research capacity for non-human preimplantation embryology, we propose to develop a Non-Human Primate Embryo Gene Expression Resource (PREGER) that can be used by any investigator to study primate preimplantation embryogenesis. Two approaches will be taken to produce large amounts of new and valuable molecular data from small numbers of embryos, along with valuable tools for further investigations. The availability of these resources and new data will permit previously unapproachable scientific questions about the primate embryo to be addressed.